Foraminous printing screen

ABSTRACT

Printing screen and method of making same wherein the printing screen includes a sheet of foraminous metal having a plurality of openings arranged symmetrically in rows and columns between which are imperforate areas, and a layer of beads adhesively secured to the imperforate areas to define the printing side of the screen.

United States Patent Reinke 1451 Oct. 10, 1972 [54] FORAMINOUS PRINTING SCREEN 2,149,977 3/1939 Morton ..l 17/ 19 X 1 846 357 2/1932 Raven ..161/l62 X 72 1 W. R k P. 14 l 1 fig 5" 0 3,060,023 10/1962 Burg et a1. ..1o1/12s.2 x 2,664,818 l/1954 Heasley ..101/128.2 [22] Filed: Dec. 3, 1969 2,955,052 10/1960 Carlson et a1 ..l01/l28.2 X 2,804,417 8/1957 Cross et a1. ..161/162 [21] 881700 3,361,058 1/1968 Michalchik ..101/12s.4

[52] US. Cl. ..101/l28.3, 96/364, 101/ 128.4, Primary Examiner-Clyde I. Coughenour 117/18, 117/33, 118/308, 161/D1G. 5 Attorney-Lloyd L. Zickert [51] Int. Cl ..B41n l/24, G030 5/06 [58] Field of Search.....101/128.2, 128.3, 128.4, 129; [57] ABSTRACT rlntln screen an me 0 0 m mg same w ereln 14:2 1 13;13 :1 12,11112141 1 P g d m d f h the printing screen includes a sheet of foraminous metal having a plurality of openings arranged symmet- [56] References cued rically in rows and columns between which are imper- UNITED STATES PA forate areas, and a layer of beads adhesively secured to the imperforate areas to define the printing side of 1,804,170 5/1931 Lassen ..l17/33 X the Screen 2,143,946 l/1939 Hunter ..l17/33 2,555,319 6/1951 Cross ..117/33 X 4 Claims, 6 Drawing Figures 7 2O //,//I I :r s l/ PATENTEDUCI 10 I972 3.696, 741

sum 1 or 3 l 3 ne 1 j 3 FIG.2

INVENTOR GEORGE W. REINKE A TORNEYS PATENIEDum 10 1912 sum 2 or s INVENTOR GEORGE W. REINKE ATTORNEYS BY y? PATENTEDnm 10 I972 I 3.696.741

SHEEI 3 BF 3 INVENTOR GEORGE W. REINKE ATTORNEYS FORAMINOUS PRINTING SCREEN This invention relates in general to a printing screen, and more particularly to a printing screen of the foraminous type, and also to a method of making a printing screen.

It is well known that printing screens of the foraminous type have long been used in the screen printing field, and it is also well known that printing screens of the woven type have long been used in the screen printing field. It is also well known that fine printing or detailed printing can be more readily accomplished with a woven printing screen than with a foraminous type printing screen. The foraminous type of printing screen is known to be made by electro-plating metal onto a matrix, such as shown in US. Pat. No. 2,287,122. While a foraminous printing screen may well serve to print designs on textiles, it is not generally suitable for printing on paper a pattern having a sharp outline. Accordingly, the woven type printing screen is normally used when printing on material other than a fabric and where some clear resolution is desired.

The present invention concerns the foraminous type printing screen and the converting of same into a printing screen of substantially improved printing resolution so that it will be acceptable for printing on materials other than fabrics. In this respect, the screen of the present invention includes a foraminous sheet of metal made by any suitable method such as by the standard electro-plating method, and a layer of tiny beads adhesively secured to the imperforate areas between the openings in the sheet.

The method of the invention includes applying a coating of solvent resisting adhesive to one side of a foraminous sheet of metal and in particular to the imperforate area between the openings, thereafter applying a layer of tiny beads onto the imperforate areas and in particular onto the adhesive coating which are locked in place on the imperforate areas by the adhesive when it cures. It is necessary to prevent the openings from closing through the application of the adhesive and/or the beads, and this may be done by blowing compressed air through the openings of the sheet from the side opposite to which the beads are mounted, during the application of the adhesive and/or the beads. Following the curing of the adhesive, in order to positively assure the securing of the beads onto the metal sheet, another coating of adhesive may be applied to the beads which runs to the bases of the beads and to further enhance the securing of thebeads onto the metal sheet.

Preferably, the beads are spherically shaped and of uniform size. The beads may be of glass, plastic, metal or any other suitable material which will withstand the conditions under which the screen is made and under which it is used.

The conventional photographically reproduced pattern may be applied to the bead side of the screen. Thus, an emulsion pattern is provided on the beaded side of the screen, and where the emulsion is present, it enhances the strength of the screen by tying together the beads within its reach. While the emulsion is applied over the beads, it will be appreciated that it flows between the beads which are bunched together by the point contact. During the printing process, as the printing ink is forced through the screen, it will be appreciated that it will run along the beads to the emulsion edges. Except where used in connection with printing on fabrics, heretofore known foraminous type printing screens will form dots on materials having ragged edges in an open area of the screen because of the contact of the open areas against the material being printed, there being no path of movement of the printing ink along the imperforate areas.

It is also well known in the art that it is not possible to have a seamless continuous screen of the woven type, such as where continuous screens are employed in rotary printing presses like that in US. Pat. No. 3,155,034. Yet, it is preferable to have a seamless printing screen for such a press. Whether seamless or not, it is recognized that a printing screen for this type of press is normally referred to as a cylindrically shaped screen or as a sleeve. It is also appreciated that a seamless or substantially seamless sleeve screen can be made by the electro-plating method resulting in a foraminous type of printing screen. As above mentioned, the printing capabilities for a foraminous type of screen are normally only accepted in the printing of textiles.

The present invention as applied to a sleeve screen permits it to be used in the printing of materials other than textiles and where better resolution is needed.

It is therefore an object of the present invention to provide an improved printing screen of the foraminous type.

Another object of the present invention is in the provision of a method for making an improved printing screen of the foraminous type.

Still another object of the present invention is to provide a printing screen including a foraminous sheet of metal having a plurality of openings arranged symmetrically in rows and columns, and a layer of beads adhesively secured to one side to define a printing side similar to that of a woven type of screen.

A further object of this invention is to provide a foraminous type of printing screen capable of supporting a thicker photo-emulsion to facilitate sharp definition in the printing operation.

A still further object of this invention resides in the provision of a foraminous type of printing screen having simulated on the printing surface a woven type of screen capable of permitting high quality of printing and fineness of printing detail by allowing the ink to flow to the edge of the image, around the beads.

A further object of this invention is to provide a conventional foraminous type of printing screen with a layer of beads on one side presenting a multiplicity of tiny surfaces similar to that defined by intersecting threads of a woven type screen to provide comparable printing qualities.

Other objects, features and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheets of drawings, wherein like reference numerals refer to like parts, in which:

FIG. 1 is a greatly enlarged plan view of the printing side of a printing screen according to the present invention;

FIG. 2 is a sectional view taken substantially along line 2--2 of FIG. 1;

FIG. 3 is similar to FIG. 1 but illustrating a photoemulsion pattern thereon;

FIG. 4 is a sectional view taken substantially along line 44 of FIG. 3;

FIG. 5 is a perspective view of a sleeve printing screen according to the present invention with the beads and openings enlarged for purposes of illustration; and

FIG. 6 is a plan view of a flat printing screen according to the invention, also with the openings and beads enlarged for illustration.

The printing screen of the invention essentially uses the foraminous type of printing screens heretofore well known thatare generally made of the well known electro-plating method For example, a copper matrix is prepared which has symmetrically arranged cavities filled with a plate resist, thereby leaving exposed parts. The exposed parts are then plated by well known electroplating methods with a suitable metal, such as nickel. Thereafter, the plating is removed from the matrix to define a perforated or foraminous sheet of metal having holes or openings arranged symmetrically in rows and columns. This method of making a sheet of foraminous metal is especially useful for making a rotary screen or sleeve screen for use on rotary presses since the matrix may be in the form of a cylindrical mandrel, wherein the completed sleeve screen is made without a seam or joint.

The foraminous type of screen may be made in various mesh counts, usually from 60 to 150 mesh. Such a screen is entirely satisfactory for printing textiles, wherein a design on the screen is applied with a photo resist, and dyes are impressed through the screen. Since these screens are not capable of printing sharp, straight lines, they are therefore not suited for printing on paper. Yet in textile printing, the ink or dye will flow around the threads of the textile which is not objectionable and which permits satisfactory use with textiles.

In order to obtain good printing quality on detailed printing work where sharp definition or resolution is desired, the taffeta weave printing screen effect is needed, where the over and under weave allows ink to pass through, while only one high spot of the weave at the intersecting threads touches the paper upon which printing is made. A sharp edgealong the emulsion is provided and the ink flows around the threads and up to the edge of the emulsion design to produce a smooth coating of ink with a sharp edge.

The heretofore known foraminous type screen, in the open area of a pattern, provides a substantial area which touches the work, and when ink is impressed through the screen, it is pulled away in such a manner as to leave an objectionable rough finish to the ink. Also the ink may be in dot form, making the edges of the final print rough and usually of a sawtooth shape, which is objectionable. It is not possible to establish a thick enough emulsion on the printing side of the screen. to create the proper type of dam against which the ink can flow, except in narrow areas, where the image resist prevents the imperforate area from touching the printing surface.

A typical foraminous type of screen of 120 mesh is 0.003 inches thick with holes about 0.004 inches. During the production of the screen, it is attempted to make the holes or openings substantially square, but the plating operation creates round holes between which are imperforate areas that are essentially flat. it may be generally considered that they holes or openings are of about the same size as the imperforate areas therebetween.

The present invention simulates the effect of a woven screen on a foraminous type of screen thathas been made by electro deposition methods, thereby improving considerably the quality of print obtainable and the fineness of detail which can be printed. The screen of the present invention is made by applying a thin coating of solvent resistant adhesive, such as an epoxy resin, and thereafter applying onto the adhesive a substantially single layer of beads of a uniform size which is substantially smaller than the size of the openings. During the application of the adhesive and/or the beads, the openings are maintained open, such as by blowing air therethrough.

Referring nowto the drawings and particularly to FIGS. 1 and 2, the printing screen of the invention is illustrated and generally designated by the numeral 10. The screen includes a sheet of foraminous metal 11 having a layer 12 of beads secured to one side.

The sheet of foraminous metal 11 may be conventionally made by the heretofore mentioned electroplating methods, wherein it includes openings or holes 13 extending therethrough and arranged symmetrically in rows and columns, and between which is an imperforate area .14. The opposing surfaces 11a and 11b of the sheet 11 are substantially parallel to eachother, although it should be appreciated that they need not be. The thickness of the sheet and the number of holes or openings per inch will vary depending on how the sheet is made and for what purpose it is to be used in a printing process.

A typical mesh foraminous sheet would be 0.003 of an inch thick, with holes 0.004 of an inch in diameter and spaced apart so that adjacent edges of holes are about 0.004 inches apart. The foraminous sheet would preferably be made of nickel, although it could be made of any other suitable metal.

The layer of beads 12 on the printing surface of the sheet changes the outer printing surface of the screen so that in effect a space is developed between the printing paper and the screen, giving the ink a chance to flow just as is possible in a woven screen, Thus, a woven screen effect is applied to one side of the foraminoussheet 11. The layer of beads 12 includes a plurality of side-by-side and generally abutting beads 15 of uniform and predetermined spherical shape. It should be appreciated that the size of each bead may not be absolutely identical, due to manufacturing tolerances, but they will be of substantially uniform diameter so that as close to a single layer of beads as possible can be applied to one side of the foraminous sheet 11. The diameter of the beads must be substantially less than the diameter of the holes or openings in the foraminous sheet, and preferably less than one-half the diameter of the holes. For example, with 120 mesh foraminous sheet, having 0.004 of an inch holes, the bead size may be between 0.0015 to 0.002 in diameter. It should be appreciated that coarse or large size beads would not be used on fine mesh, but it would be possible to use find or small beads on course mesh. As already indicated, the beads are preferably glass, although they may be metal, plastic or any other'suitable material. It

is merely essential that the beads which may be considered particles be of uniform size and substantially spherical in structure.

The beads are secured to the foraminous sheet by a solvent resistant adhesive, such as an epoxy resin, wherein a thin coat 16 of adhesive material is applied to one side of the foraminous sheets, followed by application of a layer of fine beads while the adhesive is still sticky and uncured. It is preferable to obtain as close to a single layer of beads as possible which lay on the imperforate areas 14. In order to avoid filling the openings 13, air may be blown therethrough from the inside of the screen. It should be recognized that any other suitable method of maintaining the holes open may be employed during the application of the adhesive and/or the beads.

The thin coat of adhesive material may be on the order of 0.0002 inches. This will allow the beads to be adequately secured to the foraminous sheet, while not filling the area between the beads except at the very base of each bead. In order to be sure that the beads are bonded to the foraminous metal sheet, another thin coat of adhesive may be applied over the beads, on the order of 0.0001 inches thick as illustrated at 17. The latter adhesive coating may not be necessary in all instances.

It should be appreciated that it is not necessary that the beads closest to the edges of the holes be completely clear of the holes, in that they may hang partially over the holes as shown in FIG. 2. Such will not affect the flow of ink through the screen because of the shape of the beads.

The completed screen according to the invention presents a plurality of tiny point-like surfaces 18 at the outermost ends of the beads which will if not covered by an emulsion engage against the material being printed, this being similar to the tiny surfaces defined in a woven screen at intersecting threads. Application of the adhesive and beads may be by any suitable method. For example, the adhesive may be flowed onto the surface of the foraminous sheet, and the beads may be dusted onto the surface of the adhesive.

FIGS. 3 and 4 illustrate the invention with a photoemulsion 19 applied to the printing side of the screen. It will be seen that the photo-emulsion covers the beads and openings in the area to which it is applied, and also flows downwardly between the beads to their bases. By virture of the bead layer, the emulsion thickness is substantially thicker than that possible with the heretofore foraminous type screen inasmuch as the beads furnish support for the thicker photo-emulsion. A sharp emulsion edge 20 is defined by the emulsion pattern 19 against which the ink will flow when it is pressed through the screen by virtue of the ink being able to flow around the beads 15. This will permit a sharp definition of the printed image.

The printing screen of the invention is especially useful for sleeve type or cylindrically shaped screens such as illustrated in FIG. 5, and illustrated by the numeral 21, but it may just as well be used for a flat screen as illustrated in FIG. 6 and illustrated by the numeral 22.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

This invention is hereby c l aimed as follows: 1. A printing screen of e non-woven type which presents a printing surface substantially like that of the woven type, said screen comprising, a mesh foraminous sheet of metal having a plurality of 0.004 inches in diameter openings extending therethrough and arranged symetrically in rows and columns between which are imperforate areas, and a layer of spherically shaped beads 0.0015 to 0.002 inches in diameter adhesively secured to said imperforate areas.

2. A printing screen as defined in claim 1, wherein said screen is cylindrical in form, continuous circumferentially and seamless.

3. A printing screen as defined in claim 1, wherein the adhesive on the imperforate areas is of a thickness substantially less than the diameter of the beads.

4. A printing screen as defined in claim 1, wherein of about 0.0002 inches. 

1. A printing screen of the non-woven type which presents a printing surface substantially like that of the woven type, said screen comprising, a 120 mesh foraminous sheet of metal having a plurality of 0.004 inches in diameter openings extending therethrough and arranged symetrically in rows and columns between which are imperforate areas, and a layer of spherically shaped beads 0.0015 to 0.002 inches in diameter adhesively secured to said imperforate areas.
 2. A printing screen as defined in claim 1, wherein said screen is cylindrical in form, continuous circumferentially and seamless.
 3. A printing screen as defined in claim 1, wherein the adhesive on the imperforate areas is of a thickness substantially less than the diameter of the beads.
 4. A printing screen as defined in claim 1, wherein the adhesive on the imperforate areas is of a thickness of about 0.0002 inches. 